Polydopamine Nanotubes: Multifunctional Smart Nanotransducers for Cellular Activity Modulation.

Polydopamine nanotubes (PDA-NTs) represent a recently developed and scarcely explored class of nanostructures with exceptional multifunctionality. Synthesized through a ZnO-templated Stöber-like process followed by template removal, PDA-NTs exhibit a combination of piezoelectric, photothermal, and antioxidant properties, a collection of features never observed together in a single organic nanoparticle. This work provides the demonstration of electromechanical conversion in polydopamine structures, with PDA-NTs showing a robust piezoelectric coefficient (d33 = 15.0 ± 0.7 pC/N), a property completely absent in spherical PDA nanoparticles. PDA-NTs are efficiently internalized by cells and display excellent biocompatibility; upon remote stimulation, they can modulate intracellular calcium levels via ultrasound-driven activation or near-infrared (NIR) photothermal heating. In addition, their strong antioxidant capacity mitigates oxidative stress, while controlled dopamine release (both passive and ultrasound-triggered) induces functional effects in human neural stem cells. This unique combination of mechanical and NIR responsiveness, antioxidant activity, and neuromodulatory drug release within a single organic nanostructure marks a significant breakthrough, allowing PDA-NTs to emerge as a unique class of "smart" multifunctional nanomaterials, enabling remote cellular control and offering exciting opportunities for regenerative medicine, neurostimulation, and advanced bioelectronics.